Reclosable fasteners for plastics bags and other containers

ABSTRACT

A zipper ( 10 ) for application to a film or web using cross-web techniques comprises two interengageable elements ( 12, 14 ), each having engageable hooks ( 20, 22 ), and each having an upstanding post ( 24 ) at the margin of the fastener which is engageable with a heel ( 28 ) at the opposing margin of the other element, with the respective posts ( 24 ) and heels ( 28 ) being complementarily angled ( 26 ) at their respective contact surfaces. This enables the closure more easily to resist pressure without distortion.

FIELD OF THE INVENTION

[0001] This invention relates to reclosable fasteners, otherwise knownas zippers, for plastics bags and other containers, and is particularlyconcerned with zippers intended to be applied to a film or web usingcross-web techniques.

BACKGROUND TO THE INVENTION

[0002] When a zipper strip is applied to a film or web, heat andpressure are applied to effect the welding of the zipper to the film orweb. The heat and/or the pressure can result in damage to the closure.Various measures have been adopted to try to minimise the effects of theheat and pressure. However, it can still happen that the zipper isdamaged or distorted as a result of these external influences.

SUMMARY OF THE INVENTION

[0003] It is an object of the present invention to provide an improveddesign of zipper which is resistant to distortion or damage due to thewelding heat and/or pressure.

[0004] In accordance with the present invention there is provided areclosable fastener for plastics bags and other containers, comprisingtwo elements, each element comprising at least one portion releasablyengageable with a portion of the other element, and each elementcomprising an upstanding post at the margin of the fastener which isengageable with a heel of the other element at the opposing margin ofsaid other element, wherein the respective posts and heels of the twoelements are complementarily angled at their respective contactsurfaces.

[0005] The fact that the respective contact surfaces of the posts andheels are angled or mitred enables the closure more easily to resistpressure without distortion and without the hooks being squashed. Themargins of the closure are more easily able to resist bending and tomaintain their desired supporting function.

[0006] The releasably engageable portions are preferably hookedportions.

[0007] Preferably, each of the elements of the closure is provided withtwo hooks, engageable with the hooks of the other element.

[0008] In a preferred embodiment of the invention, and with a viewparticularly to resisting distortion or damage due to heat, each of theelements is provided at or adjacent to its margins, on the face remotefrom the hook or hooks, with a pair of protruding ribs which provideadditional bulk at these marginal zones. The ribs are preferablyoverlaid each with a layer of high performance sealing/welding material,such as EVA for example.

[0009] In a preferred embodiment of the invention, a single long flangeis provided on one only of the two interengageable elements of theclosure, this flange being arranged to face the inside of the bag andbeing used for initial attachment to the film or web.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order that the invention may be more fully understood, onepresently preferred embodiment of zipper in accordance with theinvention will now be described by way of example and with reference tothe accompanying drawing which is a schematic cross-sectional viewthrough the zipper.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0011] Referring to the drawing, there is shown a zipper, indicatedgenerally at 10, comprising a first element 12 and a second element 14.The two elements 12 and 14 are generally the same as each other, apartfrom the fact that element 12 is provided with a single elongate flange16. Each element 12, 14 comprises a body portion 18 with two upstandinglegs 20 which terminate in hooks 22. The respective hooks 22 of the twoelements 12 and 14 are interengageable to make the reclosable fastener.

[0012] Each element 12, 14 also comprises an upstanding support post 24at one margin. The support post 24 is slightly longer than the hookedlegs 20, 22 so that it extends slightly beyond the tops of the legs. Theupper end surface 26 of each post 24 is tapered to provide an angledcontact surface. Facing each support post 24, on the opposing element,there is provided a heel portion 28, again at the margin. The surface ofeach heel portion 28 facing the respective post 24 is shaped, i.e.angled, to be complementary to the angled contact surface 26. As can beseen from the drawing, with this arrangement, the respective posts andheels nest with one another to provide a shape-locking configurationwhich tends to resist squashing or outward bending under vertical loads.The angled contact surfaces are able to absorb the welding pressure andmaintain their linear integrity, thus preventing the hooked legs 20, 22from being squashed or distorted.

[0013] In order to reduce the effects of the welding heat, each of theclosure elements 12 and 14 is provided with a pair of ribs 30 on theoutside face remote from the legs 20. The respective ribs 30 areprovided again at the margins of the closure, in alignment with theposts 24 and heel portions 28. The ribs 30 are provided by a thickeningof the material of which each of the two elements is composed. Becauseof the additional bulk provided by the ribs 30, they also contribute tothe resistance of the closure to deformation due to pressure. On eachrib 30 there is provided a layer 32 of a material which is ahigh-performance sealing/welding material or blend of materials, such asEVA for example. This facilitates the welding of the zipper to theencompassing web or film (not shown). The layers 32 are co-extruded withthe closure elements 12 and 14.

[0014] The single long flange 16 which is part of element 12 is arrangedto face the inside of the bag or container. This flange is used forinitial attachment to the film or web as the zipper is applied to theweb by a cross-web technique. The provision of a single long flangeprovides increased internal strength to the bag by altering the angle atwhich the load in the bag acts against the zipper closure.

1. A reclosable fastener for plastics bags and other containers,comprising two elements, each element comprising at least one portionreleasably engageable with a portion of the other element, and eachelement comprising an upstanding post at the margin of the fastenerwhich is engageable with a heel of the other element at the opposingmargin of said other element, wherein the respective posts and heels ofthe two elements are complementarily angled at their respective contactsurfaces.
 2. A reclosable fastener as claimed in claim 1, in which thereleasably engageable portions are hooked portions.
 3. A reclosablefastener as claimed in claim 1 or 2, in which each of the elements isprovided with two hooks, engageable with the hooks of the other element.4. A reclosable fastener as claimed in claim 1, 2 or 3, in which each ofthe elements is provided at or adjacent to its margins, on the faceremote from the hook or hooks, with a pair of protruding ribs.
 5. Areclosable fastener as claimed in claim 4, in which each of the ribs isoverlaid with a layer of sealing/welding material.
 6. A reclosablefastener as claimed in claim 5, in which the sealing/welding material isEVA.
 7. A reclosable fastener as claimed in any preceding claim, inwhich a single flange is provided on one only of the two interengageableelements of the fastener, for attachment to a film or web.